Too fast in the sense of 120MPH, rather than under a nice billowing
canopy.
These are used in addition to an 'analogue' alti, and common sense
(blimey, the big green thing below me is getting awfully big). Skydivers
also
often use a barometrically operated device which senses rate of change
of altitude, and triggers a small explosive charge, if necessary, to
deploy
the reserve at a given height. Many saves have been credited to these
devices, (called 'Cypress') where skydivers become forgetful, or are
knocked
unconscious. I wouldn't jump without one.

> 3. I have a friend into model rockets - how high do they get?

I was thinking that, assuming we could find the 'remains' of the rocket,
I could plug a cable in, press a button, and the onboard pic could send
it's recorded info to an LCD. Real-time telemetry would seem like
overkill!